Voltage generator

ABSTRACT

A rectifier circuit  30  of a voltage genetator  100  rectifys a alternating current signals through the use of the electromagnetic induction of a coil  11 , the rectified signals are boosied by rectifying the voltage of nodes of the coil  11  by capacitors  21  and  22 , and the voltage genetrator  100  generates a predetermined voltage by smoothing the boosted signals by a capacitor  17.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional application of application Ser. No. 09/611,948,filed Jul. 6, 2000 now U.S. Pat. No. 6,272,031, which in turn is adivisional application of application Ser. No. 09/385,439, filed Aug.30, 1999 now U.S. Pat. No. 6,104,625. The contents of each of theseapplications is hereby incorporated by reference in their entirety forall purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a voltage generator, and particularly to avoltage generator for generating a predetermined voltage through the useof electromagnetic induction, based on a received signal.

2. Description of the Related Art

A voltage generator has been applied to various devices. Of cards(hereinafter called “IC cards”) each having a semiconductor integratedcircuit incorporated therein, which have been widely used as portablestorage media in particular, it is known that the voltage generator isused in a card (hereinafter called “non-contact IC card”) capable ofperforming the transfer of data without having to use a contact terminalfor an external signal.

The voltage generator built and used in the non-contact IC cardgenerates a voltage through the use of electromagnetic induction, basedon a signal transmitted from the outside of the non-contact IC card, forexample. The voltage generated by the voltage generator is used as anoperating voltage for other circuits (such as a semiconductor integratedcircuit) incorporated into the non-contact IC card. This operatingvoltage is used as a source voltage or data to be processed by thesemiconductor integrated circuit. This type of voltage generator hasbeen disclosed in the following references:

(1) Japanese Patent Application Laid-Open No. Hei 4-23092

(2) Japanese Patent Application Laid-Open No. Hei 10-97601

As is understood from each disclosure referred to above, the voltagegenerator using electromagnetic induction is constructed so as to obtaina predetermined voltage, based on alternating current signals producedby a coil corresponding to a receiving circuit. Therefore, there may bea case in which when the distance between a coil of an external device(e.g., card reader/writer) and the coil of the voltage generatorincreases, a voltage or current based on ac signals produced by the coilof the voltage generator is not achieved to a level enough to produce anoperating voltage. There has recently been an increasing demand for avoltage generator for generating a voltage having a sufficient level asan operating voltage, regardless of the distance between the externaldevice and the voltage generator.

In order to meet the demand referred to above, an increase in the costand an increase in the area for the voltage generator may desirably beavoided to the utmost.

Further, the voltage generator may desirably generate a voltage having astable level as an operating voltage.

An object of the present invention is to provide a voltage generator forgenerating a voltage having a sufficient level as a requiredpredetermined voltage.

Another object of the present invention is to implement the voltagegenerator for achieving the above object, by reducing an increase in thecost and an increase in the area for the voltage generator to theutmost.

A further object of the present invention is to implement the generationof a voltage having a stable level as a required predetermined voltageby the voltage generator for achieving the above object.

SUMMARY OF THE INVENTION

According to one aspect of this invention, for achieving the aboveobjects, there is provided a voltage generator for generating apredetermined voltage by electromagnetic induction, based on a receivedsignal, which comprises a receiving circuit for receiving alternatingcurrent signals through the use of the electromagnetic induction, arectifier circuit electrically connected to the receiving circuit andfor rectifying the alternating current signals, a boosting circuit forboosting the signals rectified by the rectifier circuit, and a smoothingcircuit for smoothing a signal boosted by the boosting circuit tothereby generate a predetermined voltage.

Typical ones of various inventions of the present application have beenshown in brief. However, the various inventions of the presentapplication and specific configurations of these inventions will beunderstood from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter which is regarded as theinvention, it is believed that the invention, the objects and featuresof the invention and further objects, features and advantages thereofwill be better understood from the following description taken inconnection with the accompanying drawings in which:

FIG. 1 is a circuit diagram showing a voltage generating circuit orvoltage generator 100 according to a first embodiment of the presentinvention.

FIG. 2 is a diagram showing signal waveforms for explainning theoperation of the voltage generator 100.

FIG. 3 is a circuit diagram showing a voltage generating circuit orvoltage generator 200 according to a second embodiment of the presentinvention.

FIGS. 4A-4C are variation showing a diode is one comprising element ofthe voltage generator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Voltage generators of the present invention will hereinafter bedescribed with reference to the accompanying drawings. FIG. 1 is acircuit diagram showing a voltage generating circuit or voltagegenerator 100 according to a first embodiment of the present invention.Incidentally, the voltage generator 100 will be incorporated into anon-contact IC card in the first embodiment.

In FIG. 1, the voltage generator 100 comprises a coil 11 and a capacitor12 which constitute a receiving circuit, diodes 13 through 16 used asbridge-connected four rectifying devices or elements, which constitute arectifier circuit 30, forward-connected three diodes 18 through 20 andcapacitors 21 and 22 used as capacitative elements, which constitute abooster or boosting circuit, and a capacitor 17 which constitutes asmoothing circuit.

The coil 11 is electrically connected between a node A and a node B. Thecapacitor 12 is also electrically connected between the node A and thenode B. Therefore, a coil of an external device (e.g., cardreader/writer) is placed so as to be opposed to the coil 11. Whenalternating current flows in the coil on the external device side asdata to be transferred, electromagnetic induction occurs in the coil 11.Therefore, alternating current signals opposite in phase to each otherare produced at the nodes A and B.

The capacitor 12 produces a resonance phenomenon incident to the acsignals produced at the nodes A and B to thereby increase the amplitudesof the ac signals produced at the nodes A and B. While the voltagegenerator 100 does not necessarily require the capacitor 12, theinsertion of the capacitor 12 therein is effective because larger poweris obtained.

The anode of the diode 13 is grounded and the cathode thereof iselectrically connected to the node A. The anode of the diode 14 iselectrically connected to the cathode of the diode 13 and the cathodethereof is electrically connected to a node D used as an output node ofthe rectifier circuit 30. The anode of the diode 15 is grounded and thecathode thereof is electrically connected to the node B. The anode ofthe diode 16 is electrically connected to the cathode of the diode 15and the cathode thereof is electrically connected to the node D used asthe output node of the rectifier circuit 30. Namely, the rectifiercircuit 30 is a full-wave rectifying circuit in which the four diodes 13through 16 are placed in a bridge-connected configuration.

The rectifier circuit 30 comprised of the four diodes 13 through 16rectifies the ac signals produced at the nodes A and B respectively andoutputs a signal obtained by superimposing voltage levels of therectified signals on one another from the node D.

The anode of the diode 18 is electrically connected to the node D andthe cathode thereof is electrically connected to a node E. The anode ofthe diode 19 is electrically connected to the node E and the cathodethereof is electrically connected to anode F. The anode of the diode 20is electrically connected to the node F and the cathode thereof iselectrically connected to a node C. The capacitor 21 has one endelectrically connected to the node A and the other end electricallyconnected to the node E. The capacitor 22 has one end electricallyconnected to the node B and the other end electrically connected to thenode F.

With the signal at the node D, which has reached the node E through thediode 18 as the reference, the boosting circuit comprised of the diodes18 through 20 and the capacitors 21 and 22 superimposes, at the node E,the signal at the node D on the signal at the node A, which has reachedthe node E through the capacitor 21 thereby to boost the voltage at thenode E. Similarly, with the signal, which has reached the node F throughthe diode 19 as the reference, the signal at the node B is superimposedon that signal at the node F, so that the voltage at the node F isboosted. The boosted signal at the node F is outputted through the diode20 as a signal outputted from the boosting circuit.

The capacitor 17 has one end electrically connected to the node C andthe other end electrically grounded. The smoothing circuit comprised ofthe capacitor 17 is used to smooth the amplitude of the signal producedon the cathode side of the diode 20, which corresponds to the output ofthe boosting circuit. The smoothed signal is produced at the node C. Thesmoothed signal developed at the node C is outputted as a signaloutputted from the smoothing circuit. Namely, the dc voltage developedat the node C results in an output produced from the voltage generator100. This output is used as a voltage for operating other circuit (e.g.,a semiconductor integrated circuit) incorporated into the non-contact ICcard, for example.

The operation of the voltage generator 100 constructed as describedabove will be explained in more detail with reference to the drawings.FIG. 2 is a diagram showing signal waveforms at the nodes A through F ofthe voltage generator 100. In FIG. 2, the vertical axis indicates thevoltage and the horizontal axis indicates the time. Further, symbols Athrough F in FIG. 2 correspond to the nodes A through F designated atthe same symbols respectively. “0” on the vertical axis in FIG. 2indicates that the voltage is 0V. This is defined as a reference forcomparison with the respective waveforms.

When the electromagnetic induction occurs in the coil 11 as describedabove, the ac signals occur in the nodes A and B respectively. It isunderstood that the signals at the nodes A and B are opposite in phaseas designated at symbols A and B in FIG. 2. The waveforms designated atsymbols A and B in FIG. 2 respectively indicate the states of thesignals as viewed from the nodes A and B with a ground voltage on theanode sides of the diodes 13 and 15 constituting the rectifier circuit30 as the reference.

The ac signals developed at the nodes A and B are respectively rectifiedby the rectifier circuit 30 and the so-rectified two signals appear atthe node D in an superimposed state. As designated at symbol D in FIG.2, the voltage level of the signal developed at the node D is low overits entirety.

The signal produced at the node D reaches the node E through the diode18. Further, when the voltage of the node A rises, the voltage at thenode A is applied to the node E through the capacitor 21 with thevoltage at the node E as the reference. Therefore, the voltage at thenode E substantially results in one obtained by increasing the voltageof the signal developed at the node D by the voltage at the node A.

On the other hand, when the voltage at the node A drops or decreases,the signal at the node A is superimposed on the signal at the node Ethrough the capacitor 21, based on the voltage at the node E, so thatthe voltage at the node E is lowered. However, when the voltage at thenode E is lowered and reduced from the voltage applied to the anode ofthe diode 18 by the threshold voltage of the diode 18, the diode 18 isbrought to a conducting state. Therefore, since the voltage at the nodeD is applied to the node E, the voltage at the node E is not extremelyreduced. Since the diode 18 is connected to the node D in the reversedirection as viewed from the node E, the voltage at the node E is notreturned to the rectifier circuit 30 through the diode 18.

Similarly, the signal developed at the node E reaches the node F throughthe diode 19. When the voltage at the node B rises, the voltage at thenode B is applied to the node F through the capacitor 22 with thevoltage at the node F as the reference. Therefore, the voltage at thenode F substantially results in one obtained by increasing the voltageof the signal developed at the node E by the voltage at the node B.

On the other hand, when the voltage at the node B steps down, the signalat the node B is superimposed on the signal at the node F through thecapacitor 22, based on the voltage at the node F, so that the voltage atthe node F is lowered. However, when the voltage at the node F islowered and reduced from the voltage applied to the anode of the diode19 by the threshold voltage of the diode 19, the diode 19 is broughtinto conduction. Therefore, since the voltage at the node E is appliedto the node F, the voltage at the node F is not extremely reduced. Sincethe diode 19 is connected to the node E in the reverse direction asviewed from the node F, the voltage at the node F is not fed back to therectifier circuit 30 through the diode 19.

As designated at symbols E and F in FIG. 2, the voltage of the signaldeveloped at the node E is higher than the voltage of the signal at thenode D, designated at symbol D in voltage level, and the voltage of thesignal developed at the node F is higher than the voltage of the signaldeveloped at the node E in voltage level.

Incidentally, as described above, the signal developed at the node Dresults in one obtained by superimposing the signals developed at thenodes A and B, i.e., the signals supplied through the diodes 14 and 16on one another. Therefore, the waveform designated at symbol D shown inFIG. 2 results in a waveform reduced by the voltage applied to the nodeE since the voltage is applied to the node E when the voltage at thenode A is lowered and the voltage at the node E is reduced. Since thenode E is already replenished with a voltage with respect to a drop inthe voltage of the node E while similar effects are performed even onthe node F, an influence exerted on the node D is small.

The boosted signal developed at the node F reaches the node C throughthe diode 20. The signal, which has reached the node C, results in asignal smoothed by the capacitor 17 as indicated by symbol C in FIG. 2.

Thus, the voltage generator 100 according to the first embodiment iscapable of boosting or increasing the voltage of the signalcorresponding to the output of the voltage generator 100 owing to theprovision of the boosting circuit. Therefore, even if the amplitudes ofthe ac signals generated by the coil 11 are rendered small with anincrease in the distance between the coil 11 of the voltage generator100 and the coil of the external device, the voltage level sufficient asthe operating voltage for other circuits incorporated into thenon-contact IC card together with the voltage generator 100 can beensured as the output of the voltage generator 100.

Particularly when the output of the voltage generator 100 is used as asource voltage, the voltage used as the reference for permitting variousfunctions of other circuits incorporated therein together with thevoltage generator 100 is ensured. It is therefore possible to assure theoperations of other circuits built in the card together with the voltagegenerator 100 with certainty.

Since the amplitudes of the ac signals developed by the coil 11 may besmall because the voltage generator 100 is provided with the boostingcircuit, the coil may be reduced (in inductance). In this case, thevoltage generator 100 can be reduced in cost.

Since the boosting circuit is made up of several capacitors and diodesand the operations of these components are controlled by the receivingcircuit comprised of the coil 11 and the capacitor 12 and the rectifiercircuit 30, the voltage generator 100 does not include a large number ofcomponents to be added to the boosting circuit and need not have complexconfigurations for controlling the operation of the boosting circuit.Therefore, an increase in the cost and an increase in the area for thevoltage generator can be reduced to the utmost.

A voltage generator according to a second embodiment will next beexplained below with reference to the drawings. FIG. 3 is a circuitdiagram showing a voltage generator 200 according to the secondembodiment. In FIG. 3, elements of structure similar to those employedin the voltage generator 100 shown in FIG. 1 are identified by the samereference numerals to avoid the description of common elements.

In FIG. 3, P channel MOS transistors 23 and 24, a comparator 25, andresistive elements 26 and 27 which constitute a supervisory or monitorcircuit, are additionally provided as compared with FIG. 1. Othercomponents in FIG. 3 are similar to those shown in FIG. 1.

One electrode of the transistor 23 is electrically connected to a node Aand the other electrode thereof is electrically connected to one end ofa capacitor 21. Namely, the node A and the capacitor 21 are electricallyconnectable to each other through the transistor 23. One electrode ofthe transistor 24 is electrically connected to a node B and the otherelectrode thereof is electrically connected to one end of a capacitor22. Namely, the node B and the capacitor 22 are electrically connectableto each other through the transistor 24.

One end of the resistive element 26 is supplied with a signal outputtedfrom a node C and the other end thereof is electrically connected to aplus-side input terminal of the comparator 25. One end of the resistiveelement 27 is electrically connected to the plus-side input terminal ofthe comparator 25 and the other end thereof is grounded. A referencevoltage V_(REF) defined as a comparison reference is inputted to aminus-side input terminal of the comparator 25. Further, an outputterminal of the comparator 25 is electrically connected to gateelectrodes of the transistors 23 and 24 respectively.

The monitor circuit constructed as described above compares fixedvoltages obtained by fractionating the voltage of the signal outputtedfrom the node C with the resistive elements 26 and 27 and the referencevoltage V_(REF). When each fractional voltage is found to be lower thanthe reference voltage V_(REF), the monitor circuit allows a boostingcircuit to perform its boosting operation. In this case, the comparator25 outputs a signal whole voltage level is a ground voltage level(hereinafter called “L level”) therefrom.

The transistors 23 and 24 are brought into conduction according to thevoltage level of the output signal of the comparator 25. In this state,the voltage generator 200 shown in FIG. 3 is capable of performingoperation similar to that of the voltage generator 100 shown in FIG. 1.

When the fractional voltage is greater than or equal to the referencevoltage V_(REF), the boosting of the boosting circuit is prohibited. Inthis case, the comparator 25 outputs a signal whose voltage level is asource voltage level (hereinafter called “H” level”) therefrom.

The transistors 23 and 24 are brought out of conduction according to thevoltage level of the output signal of the comparator 25. In thiscondition, the voltage generator 200 shown in FIG. 3 serves so as to cutoff electrical connections between the capacitor 21 constituting theboosting circuit and the node A and between the capacitor 22constituting the boosting circuit and the node B. As a result, thevoltages at the nodes to be boosted by the boosting circuit are notboosted.

Now, the reference voltage V_(REF) is a voltage under which thecomparator 25 is capable of determining whether the voltage level of thenode C is a predetermined voltage required as the output of the voltagegenerator. In other words, when the voltages fractionated by theresistive elements 26 and 27 are lower than the reference voltageV_(REF), the voltage at the node C becomes lower than the predeterminedvoltage necessary as the output of the voltage generator. Further, whenthe fractional voltages divided by the resistive elements 26 and 27 aregreater than or equal to the reference voltage V_(REF), the voltage atthe node C becomes greater than or equal to the predetermined voltagerequired as the output of the voltage generator. The reference voltageV_(REF) may be produced from a band-gap voltage or the like, forexample.

Thus, the voltage generator 200 according to the second embodiment canobtain effects similar to those obtained by the voltage generator 100according to the first embodiment. Further, since the voltage generator200 is provided with the monitor circuit, the voltage at each node to beboosted by the boosting circuit is not boosted where the predeterminedvoltage required as the output of the voltage generator 200 issufficiently obtained. Therefore, the other circuits to which thevoltage corresponding to the output of the voltage generator 200 isapplied, can be prevented from being destroyed due to a high voltageincident to excessive boosting. It is also possible to prevent needlesspower consumption due to the provision of a clamping circuit or the likefor preventing such a destruction.

When the predetermined voltage required as the output of the voltagegenerator 200 is not sufficiently obtained due to the reason that, forexample, a coil of an external device is distant from the coil of thevoltage generator, the voltage generator 200 can increase the voltage ateach node to be boosted by the boosting circuit.

While the voltage generator according to the present invention has beendescribed above in detail, it is not necessarily limited to theconstruction referred to above.

The respective diodes that constitute the voltage generators 100 and 200shown in FIGS. 1 and 3, may be a diode-coupled bipolar transistor shownin FIG. 4(b) or a diode-coupled MOS transistor shown in FIG. 4(c), forexample. FIGS. 4(b) and 4(c) correspond to the direction of a diodeshown in FIG. 4(a) and show its connected state. Similarly, therespective capacitors may be those utilizing gate portions of MOStransistors. Further, the resistive elements may use a MOS transistornormally brought into conduction if practicable.

Further, the capacitor 21 and diode 19 shown in FIG. 1 or 3 and thecapacitor 22 and diode 20 shown in FIG. 1 or 3 are set in pairsrespectively, and these respective pairs are alternately provided inplural form. In this condition, the voltages at the nodes A and B may bealternately boosted with efficiency. Although the number of componentsfor the voltage generator increases in this case, a higher boostedvoltage can be obtained.

As the non-contact IC card, there is known one which incorporatestherein an electrically reprogrammable non-volatile memory such as anEEPROM or the like as a memory. A high voltage of about 20V is requiredto erase data from such a non-volatile memory and write data therein.The incorporation of the voltage generator according to the presentinvention into a device incorporating a memory requiring such a highvoltage therein as well as the non-contact IC card makes it possible touse the boosted voltage generated by the voltage generator according tothe present invention as a voltage for erasing data from the memoryrequiring the high voltage and writing data therein. In this case, it isunnecessary to provide a boosting circuit (e.g., a clock oscillator anda charge pump circuit) for the voltage used to erase the data from thememory requiring the high voltage and write the data therein, aside fromthe voltage generator. Thus, the device incorporating therein the memoryrequiring the high voltage can be brought into less size and cost. Inparticular, the voltage generator according to the present invention iseffective for a strong demand for its less cost as in the non-contact ICcard.

Further, the effects of the voltage generator according to the presentinvention can be obtained without providing the diode 18 or diodes 14and 16 shown in FIG. 1 or 3. Namely, when the diode 18 is not provided,the node D is electrically directly connected to the other end of thecapacitor 21. In this case, the diode 14 or 16 can prevent the feedbackof the boosted voltage at the node D (or node E) to the node A or nodeB. On the other hand, when the diodes 14 and 16 are not provided, thecathode of the diode 13 is electrically connected to the node A, thecathode of the diode 15 is electrically connected to the node B, and thenode B is electrically connected to the node D. In this case, the diode18 can prevent the feedback of the boosted voltage at the node E to thenode D. Since a voltage drop in each node to be boosted, correspondingto one diode is eliminated without impairment of the effects obtained inFIG. 1 or 3, the voltages at each individual nodes can be boosted athigher speed and effectively.

Further, the transistors 23 and 24 may utilize an N channel MOStransistor respectively. It is in this case necessary to set the voltagelevel of the output of the comparator 25 in reverse as viewed from theabove-described embodiment. In addition, bipolar transistors may be usedas the MOS transistors.

Moreover, the voltage generator may be integrated into one chip togetherwith other circuits (e.g., a circuit which uses a voltage outputted fromthe voltage generator as a source voltage or an operating voltage fordata or the like). Since, in this case, the voltage generator accordingto the present invention restrains an increase in the number of thecomponents as described above, the effects of uninterfering with areduction in chip size of a semiconductor integrated circuit due to thevoltage generator can be expected.

Thus, many changes can be made to the voltage generator according to thepresent invention if similar effects can be obtained based on operationsimilar to the present invention.

While the present invention has been described with reference to theillustrative embodiments, this description is not intended to beconstrued it a limiting sense. Various modifications of the illustrativeembodiments, as well as other embodiments of the invention, will beapparent to those skilled in the art on reference to this description.It is therefore contemplated that the appended claims will cover anysuch modifications or embodiments as fall within the true scope of theinvention.

What is claimed is:
 1. A voltage generator for generating apredetermined voltage based on an alternating signal generated by anexternal apparatus, said voltage generator comprising: a first circuithaving at least one receiving node which receives the alternating signalby an electromagnetic induction and an internal node, wherein said firstcircuit rectifies the alternating signal to generate a rectified signalon said internal node, and wherein the first circuit boosts therectified signal to generate a boosted signal; and a second circuitwhich smooths the boosted signal to generate the predetermined voltage;wherein said at least one receiving node comprises first and secondnodes, and wherein said first circuit comprises a first capacitor havingone end connected to the first node and the other end electricallyconnected to an output node and a second capacitor having one endconnected to the second node and the other end electrically connected tothe output node.
 2. The voltage generator according to claim 1, saidfirst circuit further comprising a first diode and a second diode,wherein the first diode is connected between said internal node and theother end of the first capacitor, and the second diode is connectedbetween the other end of the first capacitor and the other end of thesecond capacitor.
 3. A method of generating a voltage based on analternating signal that is obtained from an externally suppliedalternating signal by an electromagnetic induction, said methodcomprising: receiving the alternating signal at at least one receivingnode; rectifying the alternating signal to generate a rectified signal;boosting the rectified signal to generate a boosted signal; outputtingthe boosted signal from an output node; and smoothing the boosted signalto provide the voltage; wherein said at least one receiving nodecomprises first and second nodes, and wherein said first circuitcomprises a first capacitor having one end connected to the first nodeand the other end electrically connected to the output node and a secondcapacitor having one end connected to the second node and the other endconnected to the output node.
 4. The method of generating a voltageaccording to claim 3, said first circuit further comprising a firstdiode and a second diode, wherein the first diode is connected betweensaid rectified node and the other end of the first capacitor, and thesecond diode is connected between the other end of the first capacitorand the other end of the second capacitor, and wherein said boostedsignal is transferred to said output node through the diodes.
 5. Amethod of generating a voltage based on an alternating signal that isobtained from an externally supplied alternating current signal by anelectromagnetic induction, said method comprising: receiving thealternating signal at at least one receiving node; rectifying thealternating signal to generate a rectified signal output on a rectifiednode; boosting the rectified signal on the rectified node according tothe signal on the receiving node to generate a boosted signal;outputting the boosted signal from an output node; and smoothing theboosted signal to provide the voltage.
 6. A voltage generator forgenerating a predetermined voltage based on an alternating signalgenerated by an external apparatus, said voltage generator comprising: afirst circuit having at least one receiving node which receives thealternating signal by an electromagnetic induction and an internal node,wherein said first circuit rectifies the alternating signal to generatea rectified signal on said internal node, and wherein the first circuitboosts the rectified signal to generate a boosted signal; a secondcircuit which smooths the boosted signal to generate the predeterminedvoltage; and a monitor circuit which monitors the predetermined voltageand controls a boosting operation of said first circuit in accordancewith a monitoring result.
 7. The voltage generator of claim 6, disposedon a portable storage module, wherein said monitor circuit controls saidfirst circuit to boost the predetermined voltage when the predeterminedvoltage is lower than an activating voltage of the portable storagemodule.
 8. The voltage generator of claim 6, disposed on a portablestorage module, wherein the predetermined voltage is used as a powervoltage of the portable storage module.
 9. A voltage generator forgenerating a predetermined voltage based on an alternating signalgenerated by an external apparatus, said voltage generator comprising: afirst circuit having at least one receiving node which receives thealternating signal by an electromagnetic induction and an internal node,wherein said first circuit rectifies the alternating signal to generatea rectified signal on said internal node, and wherein the first circuitboosts the rectified signal on the internal node to generate a boostedsignal according to the signal on the receiving node; and a secondcircuit which smooths the boosted signal to generate the predeterminedvoltage.
 10. The voltage generator of claim 9, disposed on a portablestorage module, wherein the predetermined voltage is used as a powervoltage of the portable storage module.
 11. A method of generating avoltage based on an alternating signal that is obtained from anexternally supplied alternating signal by an electromagnetic induction,said method comprising: receiving the alternating signal at at least onereceiving node; rectifying the alternating signal to generate arectified signal; boosting the rectified signal to generate a boostedsignal; outputting the boosted signal from an output node; smoothing theboosted signal to provide the voltage; and monitoring the voltage andcontrolling said boosting in accordance with a monitoring result. 12.The method of generating a voltage of claim 11, wherein thepredetermined voltage is generated on a portable storage module andwherein said monitoring controls said boosting to boost the voltage whenthe voltage is lower than an activating voltage of the portable storagemodule.